Dishwashers, in particular dishwashers for non-commercial use, commonly are designed as front loading devices having a washing compartment that is accessible via a front door which is pivotable about a horizontal axis. Such dishwashers commonly are equipped with at least two baskets. While the lowest basket usually is supported by rollers that are mounted along the lower lateral edges of the basket so that, in order to facilitate the loading of the lower basket, the basked can be pulled out of the washing compartment onto the opened door, the upper basked usually is mounted in a drawer-like fashion at guide rails which are provided along the side walls of the upper basket.
Such rail assemblies are shown for example in DE 101 63 870 A1. In this conventional dishwasher the upper basket is held at guide rails which are mounted for a sliding movement between two pairs of guide rollers that are mounted at a side wall of the washing tub of the dishwasher. In order to allow for a telescopic movement of the upper basket, the guide rails have a C-shaped cross-section which is open towards the dishwasher basket and which accommodates rollers that are rotatably mounted at a side wall of the dishwasher basket. In this manner, the rail can move on the one hand with respect to the basket and on the other hand with respect to the body of the dishwasher.
A problem often encountered with such rail assemblies for guiding a dishwasher basket is that in order to allow for a smooth movement of the dishwasher basket with respect to the dishwasher body, there has to be provided for a certain play between the guide rollers and the rail, which play, however, can lead to noise during operation of the dishwasher, as well as to an uneven sliding movement of the dishwasher basket when being pulled out of or pushed into the washing compartment, which even may result in a temporary blocking of the displacement of the basket.
In order to alleviate these problems several proposals have been made in the prior art to apply a biasing force between the rail and the guide rollers, so as minimize the effects of the inevitable play between these parts. Thus, in EP 1 323 371 A2 it was suggested to provide for a biasing element, such as a spring element, a spring-biased bar or a spring-biased roll, which bears against a guiding surface of the rail, so as to bias the rail towards the guide rollers. The solution suggested in EP 1 323 371 A2 is disadvantageous in that since the biasing means is provided in addition to the guiding rollers such biasing means provides for additional complexity and hence increases the costs of the system.
A similar solution was suggested in DE 101 22 834 A1, wherein in accordance with a first embodiment there is provided, in addition to two pairs of guiding rollers, a biasing roller which is pressed by means of a spring element towards the rail. In accordance with an alternative embodiment, instead of providing for a separate biasing roller, the lower and/or the upper guide roller shall be mounted directly on a spring element so as to urge the roller against the rail. While the first embodiment suggested in DE 101 22 834 A1 has the same disadvantages as the solutions provided in EP 1 323 371 A2, the alternative solution with guiding rollers that are directly mounted on spring elements is technically not feasible because when mounting the guide rollers on a free end of wire spring, as it is shown in this document, the guide rollers can be deflected in any special direction and hence it is not possible to provide for a well defined support for the guide rails.